Separation of bio‐based chemicals from fermentation broths by salting‐out extraction

Abstract

The possibility of creating a biorefinery using inexpensive biomass has attracted a great deal of attention, which is mainly focused on the improvement of strains and fermentation, whereas few resources have been spent on downstream processing. Bio‐based chemical downstream processing can become a bottleneck in industrial production because so many impurities are introduced into the fermentation broth. This review introduces a technique referred to as salting‐out extraction, which is based on the partition difference between chemicals in two phases consisting of salts and polymers or hydrophilic solvents, hydrophobic solvents, and amphipathic chemicals. The effects of solvents and salts on the formation of two phases were discussed, as was the use of this method to recover bio‐based chemicals. This review focused on the separation of hydrophilic chemicals (1,3‐propanediol, 2,3‐butanediol, acetoin, and lactic acid) from fermentation broths. Diols could be recovered at a high yield from fermentation broths without pretreatment especially with a hydrophilic solvent‐based system, whereas the recovery of organic acids was slightly lower. Most of the impurities (cells and proteins) were removed during the same step. Extractive fermentations were also used for polymer‐based aqueous two‐phase systems.

Combining bio- and chemo-catalysis for the conversion of bio-renewable alcohols: homogeneous iridium catalysed hydrogen transfer initiated dehydration of 1,3-propanediol to aldehydes

“…For ionic liquids that are not sufficiently hydrophobic, the addition of salts to the aqueous phase can yield biphasic mixtures to enable oxygenated targets to be selectively extracted. [17][18][19][20] Recently this approach has been applied to the removal of 1,3-propanediol from fermentation broths. 21,22 Once extracted into the ionic liquid, the desired organic product must be isolated.…”

Enhanced Production of 2,3-Butanediol from Sugarcane Molasses

“…In fact, this problem has been encountered before when we used Jerusalem artichoke stalk and tuber as carbon source to produce 2,3-BD [12,38]. The viscosity, coloring matters, and impurities of the Jerusalem artichoke-based broth were increased, and the solid-liquid separation was achieved by the combination of centrifugation and salting-out extraction, while only salting-out extraction was enough to realize this purpose for the glucose-based fermentation broth [38,39]. With the wide utilization of biomass in the production of biochemicals, the viscosity, coloring matters, and impurities become the common problems and more efforts are required to be made on the downstream processing.…”

Phase separation in a salting-out extraction system of ethanol–ammonium sulfate

“…It resembles aqueous two-phase systems (ATPSs) composing of polyethylene glycol (PEG), hydrophilic ionic liquid (IL) or surfactant and salts [2]. However, the phase separation in SOESs is mainly attributed to the salting-out effect.…”